Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$152.48	6.185%	$161.9109	$161.91	$161.90	$161.90
Purchase #2	$58.45	5.278%	$61.535	$61.54	$61.55	$61.50
Purchase #3	$78.55	10.784%	$87.0208	$87.02	$87.00	$87.00
Purchase #4	$145.42	4.169%	$151.4826	$151.48	$151.50	$151.50
Purchase #5	$220.85	13.603%	$250.8922	$250.89	$250.90	$250.90
Purchase #6	$119.68	12.669%	$134.8423	$134.84	$134.85	$134.80
Purchase #7	$240.60	4.786%	$252.1151	$252.12	$252.10	$252.10
7 purchase totals =	$1,016.03		$1,099.7989	$1,099.80	$1,099.80	$1,099.70